1. Technical Field
The present invention relates to a high-sensitive three-plate color camera system, and more particularly, to a method of controlling a camera system which satisfies both high sensitivity and high resolution, and the camera system using the method.
2. Description of Related Art
In related art, there has been known a color camera system having a plurality of solid-state imaging device devices, which satisfies both high sensitivity and high resolution.
A known high-sensitive color camera system 300 disclosed in JP-B-7-075409 is shown in a block diagram of FIG. 11.
The high-sensitive color camera system 300 is configured to include solid-state imaging devices 302 to 304, a phase control circuit 307, a pixel addition control circuit 308, sample-and-hold circuits 310B, 310G, and 310R, and a sync signal generation circuit 311. In the camera system, pixels disposed in a horizontal direction of the solid-state imaging devices 302 to 304 are added to each other, thereby achieving the high-sensitivity characteristics. In a pixel addition process, a pixel addition control signal output from the pixel addition control circuit 308 is supplied to the B (blue) solid-state imaging device 302 and the R (red) solid-state imaging device 304, and a pixel addition control signal with a phase controlled by the phase control circuit 307 is supplied to the G (green) solid-state imaging device 303.
FIG. 12A shows an arrangement of pixels in a normal operation where the pixel addition process in a horizontal direction is not performed to the pixels. FIG. 12B shows a spatial arrangement of pixels in a case where two pixels in a horizontal direction are added to each other in the high-sensitive color camera system 300. In the camera system 300, the pixel addition control signal supplied to the G solid-state imaging device 303 is shifted from the pixel addition control signals supplied to the B solid-state imaging device 302 and the R solid-state imaging device 304 by an amount corresponding to one pixel so that the G pixels and the B and R pixels are alternately disposed one after the other. As a result, deterioration in the horizontal resolution of luminance signal components is reduced (see FIG. 12B).
FIG. 13 is a schematic diagram showing a spatial arrangement of pixels in a known color camera system disclosed in JP-A-2002-034049. In the arrangement, the G pixels are shifted from the B and R pixels in both horizontal and vertical directions, by an amount corresponding to a half pixel, respectively. As shown in Formula 1, luminance signals Y (for example, Y121, Y122, Y211, and Y212) are calculated and interpolated to produce an increased amount of luminance signals by four times as many as the number of pixels disposed on the G solid-state imaging device.Y121=0.3*R21+0.59*G21+0.11*B21 Y122=0.3*R22+0.59*G21+0.11*B22 Y211=0.3*R21+0.59*G11+0.11*B21 Y212=0.3*R22+0.59*G11+0.11*B22  [Formula 1]
(The symbol “*” represents a multiplication sign.)
In stead of producing an increased amount of luminance signals by four times as many as the number of G pixels through interpolation, the high-sensitivity characteristics is achieved by reducing the number of pixels disposed on the solid-state imaging devices to ¼ and increasing a photo-receiving area for one pixel.